1,720,982 research outputs found
Penrose Tiling Subarrays Exploiting Mixed Antenna Element Factors for Large-Scanning Phased Arrays
No full textCharacteristic Modes Analysis of a Near-Field Polarization-Conversion Metasurface for the Design of a Wideband Circularly Polarized X-Band Antenna
Get PDFA metasurface (MS) based on loop elements operating in the near field of a linearly-polarized microstrip antenna is employed to realize a circularly polarized radiated field. The properties of the loop unit cell are highlighted with the help of the Characteristic Mode Analysis that is employed for investigating the achievable linear to circular polarization conversion bandwidth and providing the guidelines for the design of the final antenna. A finite structure comprising 4×4 unit cells is tailored for achieving a circularly polarized far field within the whole X-band adopted for satellite communications (7.25 GHz-7.75 GHz, 7.9 GHz-8.4 GHz). A simple but effective single-port excitation scheme is adopted, and the overall performance are assessed by measurements on the fabricated prototype. The good agreement between simulated and measured results confirms the reliability of the proposed approach as well as the meaningful insight provided by Characteristic Modes Theory
Low Profile Dielectric Transmitarray Based on Additive Manufacturing Technology
No full textA preliminary study concerning the possibility to exploit Additive Manufacturing (AM) technologies for the fabrication of a transmitarray (TA) is addressed. More in detail, dielectric unit cells are tailored to alter the phase profile of a TA panel operating at 30 GHz
Null-Steering Antenna Design Using Phase-Shifted Characteristic Modes
No full textA novel low-cost null-steering antenna operating at 2.45 GHz is designed by exploiting an asymmetric excitation of two characteristic modes. This compact antenna allows a null shift of the radiation pattern by changing the relative phase between the two capacitive exciters (CCEs) located above the conductive plane. As a proof of concept, a prototype of the radiator has been realized by resorting to a discrete phase shifter in order to scan the null. The measured radiation patterns prove that the proposed design strategy is reliable and applicable to other kinds of structures. The manufactured antenna is capable of steering the null within a beam of 64° centered at broadside direction (θ =0°), with depth nulls greater than 18 dB
Excitation of multiple characteristic modes on a three dimensional platform
No full textThis work is a preliminary investigation of the possibility to excite a set of characteristic modes on a three dimensional object. The aim of this study is to provide guidelines for the excitation of characteristic modes on a complex platform in order to obtain a pattern reconfigurabl
Multiple characteristic modes excitation for pattern reconfigurable antennas design
No full textThe study of the Characteristic Modes (CMs) on a square conductive plane has been addressed to design a pattern reconfigurable antenna. More in detail, it is demonstrated that an efficient stimulation of suitable current modes distribution (Jn) by a proper placing of capacitive exciters over the square plate is able to provide a pattern reconfigurable capability. In particular, the positioning of the capacitive coupling exciters (CCEs) allows stimulating three current modes, whose modal excitation degree can be easily controlled. An appropriate phase shifting between the CCEs enables to control the modal excitation coefficient of the current modes, allowing the pattern reconfigurability
Characteristic modes analysis for the design of CubeSat antennas
No full textA preliminary study of the Characteristic Modes (CMs) of a CubeSat for designing an efficient radiation system is addressed in this work. In particular, the stimulation of a proper set of orthogonal current modes (Jn) supported by the CubeSat platform is investigated to achieve a broadside radiation pattern with a suitable maximum directivity and circular polarization (CP). Moreover, the possibility to scan the beam is explored by means of a multiple CMs excitation on the platform
Design guidelines for pattern reconfigurable antennas by exploiting the characteristic modes analysis
No full textA novel pattern reconflgurable antenna operating at 2.45 GHz is designed for portable devices by exploiting the characteristic modes analysis (CMA). In particular, a null-steering antenna is proposed by exploiting the current modes distribution (Jn) over a ground plane of the dimensions of a mobile terminal. To achieve this goal, two current modes (J4 and J8) are asymmetrically excited by introducing a phase difference (Δθ) between the two capacitive coupler exciters fCCEsl hosted above the conductive plane. More in detail, the position of the CCEs allows exciting only Mode # 4 and Mode # 8, related to the current modes J4 and J8, respectively. The phase difference (Δθ) allows controlling the level of the excitation of these modes and obtaining the null-steering antenna in the y-z plane. As a proof of concept, a discrete phase shifter that employs several pin diodes has been designed in microstrip technology in order to obtain a subset of the phase differences. The radiation patterns prove that the proposed design guidelines are reliable and applicable to other kinds of structures
Advantageous Exploitation of Characteristic Modes Analysis for the Design of 3-D Null-Scanning Antennas
No full textA novel design strategy for realizing 3-D null-scanning antennas by resorting to the characteristic modes theory is described. By exploiting the variation of the excitation degree of the current modes ( over the investigated platform, a null of the pattern can be placed in any desired direction in the upper hemisphere. A rectangular conductive plane has been taken into account as test case to validate the design strategy. Design guidelines are provided for selecting and placing the proper exciters in order to realize the suitable excitation of the current. Measurements on a realized prototype are in a good agreement with simulations, confirming the reliability of the proposed approach
Characteristic modes analysis for pattern shaping of handheld platforms
No full textThe effects of introducing a phase-shift in the characteristic modes (CMs) of a rectangular conductive plane have been investigated. More in detail, a careful characteristic modes analysis (CMA) has been carried out in the aforementioned conditions to verify the possibility of significantly altering the shape of the overall radiated pattern. Among all the CMs, only two radiating modes (Jn) have been selected to achieve a pattern-reconfiguration ability. In particular, by a weighting linear superposition of only these two radiating modes over the conductive sheet, it is possible to realize a null-steering antenna in a principal plane. As proof of concept, a prototype of the proposed antenna has been realized and measured. The obtained results present a good agreement with the simulations and prove that the proposed design guidelines are reliable and also applicable to other kinds of structures
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